The present invention pertains to the field of p-aramid pulp and its use.
Processes to manufacture p-aramid pulp by fibrillating chopped p-aramid fibers are known. Furthermore, it is known to use p-aramid pulp to manufacture friction materials, gasket materials and friction papers. P-aramid pulp exhibits a morphology which consists of stems of the chopped fibers from which the pulp was manufactured and of fibrils extending from each of the stems. In the mentioned products of p-aramid pulp its fibrils hold together the components of the respective compositions which constitute the respective product, for example the components constituting a friction material, like a brake pad. Said “holding together capability” of p-aramid pulp is characterized by a high filler retention which for p-aramid pulp of Type 1099 is the range from about 60% to about 85%.
WO 2006/012040 describes an acrylic and para-aramid pulp for use as reinforcing material comprising:    (a) irregularly shaped, acrylic fibrous structures comprising acrylonitrile units, the structures being 10 to 90 wt. % of the total solids;    (b) irregularly shaped, p-aramid fibrous structures being 10 to 90 wt. % of the total solids; and    (c) water being 4 to 60 wt. % of the entire pulp,
whereby the acrylic and the p-aramid fibrous structures having stalks and fibrils where the acrylic fibrils and/or stalks are substantially entangled with the p-aramid fibrils and/or stalks. WO 2006/012040 describes a process wherein p-aramid staple fibers are provided. Furthermore acrylic staple fibers are provided. Then the p-aramid staple fibers and the acrylic staple fibers are mixed at a solids concentration of 50 wt. % p-aramid staple fibers and 50 wt. % acrylic staple fibers to form a slurry. The slurry is pumped through a series of three refiners. The refiners simultaneously fibrillate, cut and masticate the acrylic fibers and the p-aramid staple fibers to form a refined slurry. This refined slurry is dewatered to a moisture content of 50 total wt. % for wet pulp. The wet pulp is pressed in a mechanical press to further remove water; and the pulp is then fluffed to better separate the wet pulp. The fluffed wet pulp is then dried to approximately 8 wt. % moisture.
WO 2011/062980 describes a paper comprising carbon floc, p-aramid floc, p-aramid pulp, and m-aramid fibrids. The composition of the paper is 40 wt. % carbon fiber floc, 15 wt. % p-aramid floc, 30 wt. % of p-aramid pulp, and 15 wt. % m-aramid fibrids.
However, there is an everlasting demand to increase the green strength of p-aramid pulp and consequently the strength of the products containing p-aramid pulp.